This application claims priority from Korean Patent Application No. 2001-0060045, filed on Sep. 27, 2001, the contents of which are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates generally to an apparatus and a method for separating a cull generated in a molding process during semiconductor assembly.
2. Description of the Related Art
In order to meet increasingly-demanding packaging requirements for newer generations of electronic products, the industry is expending significant effort toward forming smaller and thinner chips. Smaller and thinner chips are needed to meet the industry demand for high packing density in high-speed, multi-functional semiconductor devices.
As part of this trend, the industry has introduced Ball Grid Array (BGA) packages that are small yet have high-pin counts. These BGA packages are also easy to mount. Among such packages, tape ball grid array (TBGA) packages, which use a thin tape circuit board, have caught the attention of the industry.
In general, to form a TBGA package, multiple chips are mounted on a tape circuit board. The chips are then molded and separated into individual semiconductor chip packages. The TBGA package can be fabricated having improved quality with low manufacturing costs using a simple process.
The TBGA package assembly process is different from the conventional semiconductor assembly process because of the structural characteristics of the TBGA package. Conventional semiconductor assembly processes typically include a molding process for encapsulating a semiconductor chip that is physically supported and electrically interconnected by a lead frame and a printed circuit board (PCB).
FIG. 1 is a cross-sectional view of a PCB supported semiconductor chip during a conventional molding process. In the conventional molding process, represented in FIG. 1, the PCB having the semiconductor chip is placed between molding dies 120. The molding dies 120 form a cavity 125 shaped to form a package body.
A thermoset epoxy resin 129, such as an epoxy molding compound (EMC), is injected into the cavity 125 and then cured in the cavity 125. The epoxy molding compound 129 is typically provided through one pot 127 having a plurality of cavities.
After the molding process is completed, a portion of the cured epoxy molding compound 129 remains in area through which it was supplied to the chip. This unnecessary molding compound, called xe2x80x9ccull,xe2x80x9d must then be removed through a cull separating process. The cull separating process is called a xe2x80x9cde-gatingxe2x80x9d process because the gate portion, through which the epoxy molding compound 129 was provided to the cavity 125, is removed.
FIG. 2 is a cross-sectional view of semiconductor chip packages illustrating a conventional cull separation process.
Referring to FIG. 2, the cull separation process is performed on molded parts 110 to which the cull is connected. The molded parts 110 are mounted on frame support blocks 150 arranged on both sides of the cull 115. A cull support block 140 is located between the frame support blocks 150, and a cull pressing block 180 is located above the cull support block 140. The cull 115 is held between the support block 140 and the cull pressing block 180.
A pressing means 170 is raised to contact and exerts pressure on the lower side of the outer end of the frame support blocks 150. The pressing means 170 causes each of the frame support blocks 150 to rotate a predetermined angle about a hinged axis 153 thereof, thereby rotating the molded parts 110. The rotary movement of the molded parts 110 snaps a weak portion of the molded part 110 adjacent to the gate between the package body 112 and the cull 115.
The pressing means 170 and the frame support block 150 are then returned to their original positions, and the molded parts 110 are transferred to a processing area. The separated cull 115 is transferred horizontally to a predetermined position and discarded.
Although this conventional cull separating process may be suitable for use with PCB-mounted BGA packages, it is not suitable for use with tape circuit board mounted TBGA packages.
FIG. 3 is a cross-sectional view of cull 115 generated in a TBGA package assembly process. Referring to FIG. 3, because the tape circuit board 111 is thin, it is attached to a carrier frame 113 having a predetermined thickness. The carrier frame 113 is made of stainless steel (SUS), FR-4 and copper. As shown, after the molding process is completed, the cull 115 is generated on both the tape circuit board 111 and the carrier frame 113. Because of the step-like portion A between the tape circuit board 111 and the carrier frame 113, it is difficult to remove the cull 115. If the cull 115 becomes stuck in the step portion A, for example, the above-described cull separating process will be unsuccessful, resulting in cull defects.
An apparatus for separating a cull from a molded part including a chip mounted on a tape circuit board is provided according to an embodiment of the present invention. The apparatus includes a cull support block for supporting a cull and a cull holder for clamping the cull. The cull holder is disposed above the cull support block.
The apparatus further includes a frame support block for mounting a molded part and a frame holder for pressing the molded part against the frame support block to fix the molded part thereon. The frame support block is hinged on a first axis near the cull support block. The frame holder is hinged on a second axis near the cull support block.
The apparatus also includes a pressing means configured to move downward against a distal end of the frame holder to cause the frame support block and the frame holder to rotate about the first and second axes, respectively, to separate the cull from the molded part.
In accordance with another aspect of the invention, a method for separating a cull from a molded part of a package is provided. The method includes: (a) mounting a molded part on a frame support block rotatable about a first axis, the molded part including a chip mounted on a tape circuit board; fixing the cull in place between a cull support block, on which the cull connected with the molded part is placed, and a holder block, the holder block disposed above the cull support block, (c) fixing the molded part in place between the frame support block and a frame holder, the frame holder rotatable about a second inner axis; and (d) moving a pressing means down against the frame holder to rotate the frame holder and the frame support block about the first and second axes, respectively, to separate the cull from the molded part.
In accordance with yet another aspect of the present invention, the method may further comprises: (e) lifting up the pressing means; (f) lifting up the frame holder; and (g) removing the cull using a suction means.
In accordance with still another aspect of the present invention, the pressing means is repeatedly raised and lowered at least twice during the separation of the cull from the molded part.
In accordance with one aspect of the present invention, the method further comprises (f) lifting the cull support block up to a predetermined height before removing the cull.
In accordance with another aspect of the present invention, fixing the molded part in place between the frame support block and a frame holder comprises moving down the frame holder to press the molded part.